低温季节大坝混凝土冷却水管周围应力应变监测现场试验

大坝混凝土力学性质受诸多因素影响,变化规律复杂,最新研究表明:不同的温度条件对混凝土的变形规律有着明显的影响.对此,在西南某混凝土特高拱坝冬季混凝土浇筑现场,结合冷却水管周围不同位置处单支应变计测值和每支应变计附近同样温度条件下设置的专用无应力计监测的该温度条件下自由体积变形,通过建立大坝无应力计统计模型分析无应力计测值得出混凝土热膨胀系数,并分离出自生体积变形,采用考虑混凝土徐变特性的计算程序,将应变计测值转化为实际应力以分析冷却水管周围不同部位混凝土应力分布.试验结果表明:由于该大坝采取"小温差、早冷却、缓慢冷却"的通水冷却方式,在现有的通水冷却方案下,冷却水管周围混凝土应力不大;该试验能给现场混凝土冷却通水方案以及防裂施工提供指导,为关键部位混凝土温度应力仿真反馈分析提供实测资料.

Field test on stress-strain monitoring around positions of cooling pipe in dam concrete under low temperature

Pipe cooling is an important method in the process of temperature control construction of the mass concrete;however,pipe cooling,which is closely linked with the durability of concrete,is a double-edged sword,and is concerned by engineering construction parties.Actually,the mechanical properties of mass concrete is influenced by many factors;it is shown by the latest research that different temperature conditions have significant influence on the deformation of mass concrete.Based on this,for a extra-high concrete arch dam construction site in Southwest China,combined with the measurement value monitored by single strainmeters located around the different positions of cooling pipe in mass concrete,and the measurement value monitored by free-stressmeters,located on the positions that under the same temperature condition with correspondent strainmeter,a statistic model of stress-free measurement value was established to get the thermal expansion coefficient and separate the autogenous deformations of different positions,a calculation program that considering the creep characteristics of concrete was adoped to convert the measurement value of strainmeters of different positions around cooling pipe into stress;thus,the stress distribution of concrete around cooling pipe could be analysed.It is indicated by test results that: under the existing scheme of pipe cooling of dam concrete from earlier age with smaller temperature difference and longer time,the stress value of concrete around cooling water pipe stress was low;the test not only provided a guidance for water cooling scheme and anti-crack constructions,but also provided measured data for the key part of concrete temperature stress simulation feedback analysis.